Perfume Mythbusters: Skin Chemistry


If there is any phrase used in talking about fragrance that bothers me, it is “skin chemistry”. People will talk about how their skin chemistry makes a perfume smell different as if it is something quantifiable. As a scientist and a chemist calling it this is just a myth because there is no proof it exists and it darn tootin’ isn’t chemistry; more like physics.

Let’s deal with the obvious first. Does perfume smell different on different people? Yes, it does. The reason for that has nothing to do with some chemical reaction taking place on the skin. It has more to do with the lack of a balanced level of moisture on the skin.

Most of us do things which actively make our skin too dry by stripping the protective oils. In the winter indoor heating has no humidity. The biggest place it gets lost is in the shower. The shower is ground zero for your skin the hot water, the soap you use, and the kind of scrubbing implement can all conspire to deprive your skin of its beneficial oils. When do most of us apply perfume? Fairly soon after we shower. Before the skin has had a chance to replace what has swirled down the drain. The effect this has is the larger molecules used in a perfume are closer to the oils you just removed. What happens? Those oils go deep into thehair follicles where the sebaceous glands which produce body oils are located. This is what people who say their skin “eats” perfume are describing. These larger molecules seemingly disappear. They don’t really. They eventually rise back to the surface as the body replenishes the natural oils from below.

skin anatomy

There is a solution to this and that is using a good moisturizer right after you finish toweling off after a shower. You can replenish with something other than your perfume. If you moisturize the places you apply perfume soon after you come out of the shower, you will see a marked improvement in the way you wear your perfume. I’ll even share my tip for making moisturizing even more effective. I use an unscented moisturizer. After I put some in my hand I spray some of the perfume I plan on wearing into the moisturizer and then apply it to my skin. This not only replenishes what I lost in the shower it also acts sort of like a primer before the real application of perfume takes place.

Now let’s get to the chemistry part of this. There are two things we consume as humans which have been documented to produce a smell on our skin. One is sulfur containing foods, garlic being the most common. The other is alcohol as in alcoholic beverages. You can conceivably have some sulfur containing compounds on your skin if you just ate a whole roasted bulb of garlic. Then if you decide to add a perfume on top of that things are probably not going to go well. But that is not chemistry there is no reaction going on between the sulfur containing molecules and the fragrance molecules. Instead what you have done is a poor job of layering by adding your favorite perfume over your natural “Eau de Garlic”. You can do a better job of this by not eating that whole bulb of roasted garlic and just picking two of your favorite perfumes to layer. Alcohol secretes alcohol onto the skin and strong spices like cumin containing curries can also linger in natural body oils. Let me tell you as a chemist none of these actually react with any of the molecules in your perfume. There is zero chemistry happening.

The myth of skin chemistry is really a story of moisturization and diet. If you’re looking for a more correct phrase start calling it “skin physics”

Mark Behnke

Perfume Mythbusters: Hypo-Allergenicity of Natural Oils

As a scientist one of the more pervasive myths in perfumery is the one which says natural essential oils are hypo-allergenic. The myth goes that if it comes from nature instead of a chemistry lab it must be benign. It stems from this phobia many have about the word chemical. When I first moved to Boston I worked at a food co-op once a week. When I arrived for my shift one week there was a big display holding bags of decaffeinated coffee. On the sign above it was this, “We don’t use any chemicals to decaffeinate our coffee, only water.” I stood there laughing as I realized that right there in that simple statement was all that needs to be said about chemical versus natural. Water is a chemical made up of two atoms of hydrogen attached to one atom of oxygen. It is easy to understand that people associate the word chemical with dangerous and the word natural with safe. After all nature is safe, right? Just don’t attempt to clear out a bunch of poison ivy from your yard without the proper protection. Natural is not so nice if you get any of that on you. In fact if you do get some on you it is likely you will slather on a chemical mixture of zinc oxide and ferric oxide more commonly called Calamine Lotion.

The natural is good and the synthetic is bad paradigm exists in perfumery. There is the idea that a synthetic ingredient in a perfume has a greater ability to cause a skin reaction or a headache. The natural product is thought to be more pure with less chance to cause a physical effect. Just as with poison ivy and calamine the opposite is true. I am going to use Geranium Essential Oil versus the synthetic molecule Geraniol as my examples. The first thing you have to realize is Geranium Essential Oil is not just one single molecule it is literally dozens of molecules. In the graph below you see what is called a gas chromatograph trace of geranium essential oil. Each peak you see in the figure represents a molecule contained in Geranium Essential Oil. The bigger the peak the more there is of it. You see at the top of the figure that most of the major peaks have been identified as specific chemicals well-known in perfumery.

geranium essential oil gc

Graph from Sigma-Aldrich

As you can see below here is the gas chromatograph of synthetic Geraniol. One single pure peak and nothing else. In the previous graph is it is peak number 14.

Geraniol GC

Graph from

Here is the fallacy in the natural is good synthetic is bad myth. If you find Geraniol is an ingredient which bothers you then that single ingredient is easy to avoid just by looking at the label. But if Geraniol bothers you and you take out an all-natural perfume of geranium containing Geranium Essential Oil you should have the same reaction. Now if you’re fine with Geraniol but not Linalool (peak 8 on the trace above) you can see the natural essential oil might present a problem for you. Especially if you are someone who prefers unscented bathing products as Linalool is one of the more common fragrance synthetics used in that sector. This is why an all-natural ingredient has way more things contained in it which might cause a bad reaction.

Before I finish this installment I also want to use these two gas chromatography traces to make another very important point. When the government agencies concerned with protecting the consumer from being exposed to potential allergens they cite single molecules as the cause. When they ban or restrict the use of a single molecule you think okay they’ll use an alternative. You’re right the perfumer who uses synthetics has much more latitude to find similar properties in another synthetic. What if let’s say Geraniol was to be banned. Would that mean that Geranium Essential Oil is also banned? It should be it has a high concentration of Geraniol. That is the possible very serious consequence to the use of natural oils if this governmental interference continues.

Finally I am thankfully free of any reaction to any perfume ingredient I have encountered. I can just judge a perfume on whether it does its job. Essential oils because of the wonderful complexity of their composition provide a richer experience than the simple single molecule ever could. If you want to know why natural perfumery continues to fascinate me so much it is because the talented perfumers working with an all-natural palette are using one-of-a-kind materials in fascinating perfumes. As for being hypo-allergenic that’s a myth.

Mark Behnke

Perfume Mythbusters: The Expiration Date

One of the more common questions I get is, “Can perfume go bad?” The answer to that is yes. The corollary to that question is one of the more pervasive myths as I often will get the follow-up, “How long will my perfume last?” The answer to that is not as simple but in >95% of perfume on the market if you store it properly the answer is for a very long time. Perfume is not like milk and does not spoil after a set amount of time no matter what.

It is the first question which leads to the inaccurate assumption of the second. You can find a bottle of perfume which smells bad, or off, but it probably has nothing to do with time and much more to do with how it was handled. There are three enemies of perfume in the bottle; temperature, light, and oxygen.

If a perfume is stored at elevated temperature it will cause many of the more volatile components, usually the top notes, to evaporate. This leaves the less volatile notes behind and that completely changes the smell. This can happen very quickly if you keep the perfume above 90F/32C as things like aldehydes will be gone very quickly. Store your perfume below 65F/18F and this doesn’t happen very quickly. A perfume stored at this temperature will still have much of what you enjoyed when you first bought it.


Light, particularly sunlight, is the real enemy of perfume. Sunlight is ultraviolet radiation and many of the molecules used in perfumery can react with UV radiation and chemically change to something less pleasant to smell. If you store your perfume on a windowsill which gets direct sunlight this process can happen pretty fast. Keep your perfume out of the sunlight and it really doesn’t happen at all. Regular fluorescent light doesn’t have the same effect as sunlight and while I would still recommend keeping your perfume out of the light entirely it is the sun that does the most damage.

The first two things can easily be controlled by anyone just storing their perfume properly. The last thing which will have an effect is oxygen. The presence of oxygen happens as you use your perfume. The more you use it the more of that empty space in the bottle contains oxygen from the air. Now where temperature and sunlight can damage a perfume fairly rapidly oxygen does it much slower. One reason is the air in the bottle is only interacting with the surface of the liquid in the bottle. That is a very small surface for things to be happening. Compare that to light or temperature which interact with all of the liquid in the bottle. If there is any slight truth to the idea of an expiration date it is probably that the more you use a fragrance the more you keep adding oxygen and allowing for it to slowly interact with the perfume. Let me stress again this is a very slow process, we are talking years not months.

The answer to the question “Does perfume have a definitive expiration date?” is “No!” Any perfume you will have for a very long time will eventually change. That is a process which will take many years before it is apparent. So don’t feel like you need to use your favorite perfume up before it spoils that is just a myth.

Mark Behnke

Perfume Mythbusters: Vintage Perfume


I’m not sure if there are distinct stages of being a perfume lover but there are many common experiences we all share. One of those is trying a “vintage” perfume. What I mean by that is an original bottle of a classic perfume that is over 10 years old and often is as old as 50-60 years. The moment of trying your first vintage perfume is usually followed with a statement along the lines of, “they just don’t make perfume like that anymore”. When it comes to certain ingredients that is definitely true especially now scarce to find authentic ambergris or real musk from the musk deer. There is also another part of the equation too as many who love vintage fragrances love the depth and subtle power inherent in these older bottles. There is then a belief that what they are smelling is somehow truer than a modern version, that is the myth I am here to bust this month.


Coffee Flower Macerating in Jojoba Oil

When you are smelling an older bottle of perfume you have to take into account what has been going on over the years in that bottle. One thing that has been going on is continued maceration. When making a perfume which is high in natural ingredients there is a phase of the process called maceration. What this means is once the perfume concentrate is diluted in the desired solvent, usually alcohol, it is left to sit for a number of weeks at reduced temperature and away from light. What this allows for is these natural materials to reach a steady state where the perfume reaches consistency of odor profile. As I’ve mentioned in the past natural raw materials are not one molecule they are actually mixtures of often hundreds of different molecules. When these are combined with other natural raw materials and diluted there needs to be a settling out period. This is most often done on as large a scale as possible. The perfumer will check over time until the blend reaches a congruency from three or four different samples over different days. At this point it is transferred to a bottle. Now if the perfume is all synthetic this process is totally unnecessary as those are single molecules and need no settling out. While the early maceration is done on a large scale it does not stop once it is in the bottle. Especially when we are talking time frames of tens of years. Maceration is now a much more gradual process but when measured over many years it is still going on. This is what most often produces the softness many remark upon when trying a vintage perfume. Just like a fine Bordeaux wine a 1961 vintage is much smoother than a 2011 vintage. Time does smooth out all things. The continued maceration also accounts for the blurred less definitive transitions also found in vintage perfumes.

1950's shalimar

This sealed bottle from the 1950's was filled right to the neck when new, notice the gap now because of evaporation

Second is good old evaporation of the top notes. Top notes by their very nature are meant to be volatile and the idea that any of these still remain in a perfume that is ten years old stretches the concept of simple physics. Even if the bottle is sealed once the top notes begin to evaporate they are now in vapor form and if there is even the slightest gap out they will go. To my knowledge there is no vintage perfume which has been so meticulously sealed as to prevent this most basic of processes from happening. The effect this has when smelling a vintage perfume is you get right down to business and go straight for the heart and base notes. This is probably what gives the impression that vintage has more depth because you aren’t distracted for a second by any top notes because they are no longer there.

baccarat shalimar bottle

Vintage Baccarat Shalimar Bottle half-filled with air and clear to let light through

Third is if the bottle has been opened at all or exposed to sunlight for any period of time. Oxygen and sunlight are the natural predators of many perfume molecules converting them into all manner of things. Some of which still smell good and some which definitely don’t. It is either, or both, of these twin plagues which make a perfume go “off”. In the best case it can still leave something behind which smells good but anything like what it smelled like when it was put in the bottle, not likely.


Patricia de Nicolai

For me one of the most eye-opening experiences to this phenomenon was when Patricia de Nicolai of the Osmotheque exposed me to the versions of some of my favorite older perfumes from the Osmotheque. Through the help of the perfume companies the Osmotheque has original formulae for many of the classic perfumes and makes fresh new batches of them for their library. As I experienced these fragrances in their complete glory with top notes intact and lively paired with the heart and base notes in the vitality of their youth I realized these were the real vintage perfumes. We had a group experience of this at Esxence as we had an Osmotheque version of Edmond Roudnitska’s classic Rochas Femme. Everyone was surprised at how different it was to any version they had tried previously. If you love vintage perfume you must go to the Osmotheque and really smell the vintage perfumes you love it will give you a whole new appreciation for them.

I am not saying vintage perfumes are not lovely in their own right.  They are also not really anything like the original fragrance put in the bottle you own either. That is the myth of vintage perfume.

Mark Behnke

Perfume Mythbusters: Olfactory Fatigue and Coffee Beans


You see them on every perfume sales point counter, a small glass container full of coffee beans. Why are they there? Ostensibly they are supposed to provide an olfactory palate cleanser and help stave off olfactory fatigue. Except all of that is Perfume Myth of the highest degree as the nature of olfactory fatigue and whether coffee beans have any effect on the supposed saturation of your smell receptors is just nonsense.


Let’s deal with Olfactory Fatigue first. Olfactory Fatigue actually has a high falutin’ name, Olfactory Habituation. Olfactory Habituation is the ability of your olfactory system to take any initially strong, and here is the important part consistent, smell and deal with it by taking it in as part of your normal background. It is why when you wear your scent of the day once it has settled down to the long-lasting consistent basenotes it has now started to attain that level that it gets pushed to the background. The larger molecular weight molecules especially seem prone to this and this is also why someone might say you smell nice at a point in the day you think your fragrance is gone. This has components of psychology as well as biology attached to it as well. Therefore Olfactory Fatigue probably does happen during the course of a day wearing one particular fragrance.

But when you are out sniffing new perfumes or on a sniffathon with friends you are producing stimuli left and right but they are different stimuli. Your nose has the ability to perceive infinitely and when you are sniffing things there is no limit to what you can sniff from a biological standpoint. From a psychological standpoint it is more akin to the kid in the candy store syndrome as you have a bounty of options and you just don’t feel like smelling one more strip. You can be psychologically fatigued but your nose is ready to go if you want to try one more fragrance.

alexis grosofsky

Dr. Alexis Grosofsky (Beloit College)

This is where the coffee beans supposedly come in. The sales person will hand them to you and tell you they will prepare you to enjoy the next fragrance after “resetting” your nose. Without any science to back it up does that even make any sense? A whiff of strong coffee beans “resets” your nose. What if I just smelled Thierry Mugler A*Men Pure Coffee wouldn’t having snorted some coffee beans distort that scent? Thankfully Dr. Alexis Grosofsky of Beloit College’s Department of Psychology has provided some science to prove that coffee beans have no effect on cleansing your olfactory palate. (The abstract of her research can be found here) She exposed subjects to three different drugstore fragrances. Then they either smelled fresh air, coffee beans or lemon slices. Then they were given the same three scents plus one new one and their task was to identify the new one. The result was the group of subjects that smelled fresh air or lemon slices had a near identical success rate of those who smelled coffee beans. Proof that coffee beans are a prop which carry no value whatsoever.

So what should one do when out sniffing and one wants to “reset” their nose? The answer is right in front of you and in the second paragraph. You are always performing Olfactory Habituation to your own natural smell. That ability to push your natural smell to the background sets the baseline against what any other olfactory stimuli has to compete against. If you want to reset your nose take a deep breath of a patch of, unperfumed, skin. This is the technique I use and if you’ve ever been with me I have an almost OCD ritual of sniff the strip, stick my nose in the crook of my elbow, and sniff the strip over again; repeat as desired. I have done this at some of the biggest perfume events and have sniffed as many as 50 scents in a day and the only thing I weary of is smelling bad perfume.

Next time you are out and about remember coffee is for drinking not for perfume plate cleansing.

Mark Behnke

Perfume Mythbusters Love Potion No. 9?

One of the more pervasive fallacies when it comes to fragrance is the idea that there is a magic elixir that when worn will cause the object of your desire to fall madly in love with you, or in lust with you. I can’t say I am immune to the sentiment as the first bottle of perfume I owned was Jovan Musk. Why? Because at the age of thirteen the ads intimated that women were crazy about men who wore musk. Of course Hai Karate intimated I would need a black belt to fend off the women if I wore that. What I found out pretty quickly was it wasn’t the way I smelled that lead to success with women it was a lot of other things of which fragrance was just a component.


For many years this always seemed like a concept held exclusively by men, and women were above this kind of simplistic thinking but the recent release of Le Premier Parfum changes that. Le Premier Parfum allows the chakra associated with sex to open and in their press materials they flat out say, “Le Premier Parfum is not merely a fragrance, but an aphrodisiac.” So much for the more evolved gender. The two women behind the brand have been giving interviews urging women to, “wear it responsibly.” I guess that is their version of safe sex. This is as nonsensical as the idea of Creed Aventus causing women to lose their senses and drape themselves on the man wearing it.


The truth of this is there is not one scientific study which has ever shown any particular scent to immediately cause the object of one’s desire to go weak in the knees and let their chakras do the talking. A lot of the confusion comes from the idea of pheromones. In the insect world pheromones have been well studied and proven to exist. These substances are used to convey a lot of specific primal information from alarm, to a trail to follow back to food, and yes, sex. So because the bees do it the suggestion is so should we humans. Except there has never been any human pheromone identified to do what it does in the insect kingdom. Of course that doesn’t stop perfumes from claiming they have the magical non-existent pheromone in their fragrance. The bottom line is there has been no unequivocal scientific proof that a human pheromone exists and there are certainly none in the fragrances which claim to have them in them.

When it comes to scent and how we perceive others there have been some interesting studies which show when a woman wears grapefruit fragrances she is perceived as much younger. A very recent study has shown the smell of cedar has the opposite effect when it comes to men with people seeing a man as older than his age when wearing a cedar fragrance. The real point is that fragrance does have the ability to shape our opinion of others but not to cause them to go all googly eyed and become one’s fawning acolyte for a night. That is why when searching for the mythical Love Potion No. 9 instead look for the fragrance which complements your personal style. It is the complete package which is the real attraction between people and your fragrance is part of that package but most of the rest of the work is up to you.

Mark Behnke

Perfume Mythbusters: The Silence of the Molecules


There are some widely held ideas out on the interwebs and some of them even came from before we had this worldwide connectivity. For some of these I am going to become an olfactory version of Adam Savage and Jamie Hyneman television’s Mythbusters. Imagine I have replaced my regular fedora with a beret like Jamie’s and off we go.

As a research chemist one of the funniest things I have heard over the years from Sales Associates after applying perfume to the wrist pulse points, “Don’t rub your wrists together you’ll bruise the molecules.” Now I know most people have a natural reticence when it comes to chemistry and all those atoms and molecules. Certainly the frequency with which I am greeted with “I hated chemistry in school.” when I tell people I’m a chemist lets me know the majority aren’t so jazzed to know about the molecules in their everyday life. So when you’re told that rubbing your wrists together somehow hurts the molecules some can think, maybe it could be true. The main reason that people have believed this to be true is that when you rub your wrists together you are changing a couple of things about the way the perfume is meant to be experienced but trust me you’re not bruising the molecules, you’re not even making them uncomfortable.

If you wanted to bruise a molecule what you’re really saying is you want to break the bonds between the atoms that make up that molecule. When I want to do that in the laboratory it takes energy, actually it relatively takes a lot of energy. I have to use heat, other chemicals, ultraviolet light, even microwaves sometimes; to break open a molecular bond so that it is available to react with another molecule. The amount of friction you would have to apply by rubbing your wrists together would probably damage your skin before the first molecule even felt a little queasy.


Why this myth persists is that the perfume does develop differently when you rub your wrists together but it has nothing to do with molecular mauling. It has more to do with the physical effect of evaporation.

The perfume pyramid in a very, very basic way is just an arrangement of molecules with different evaporation rates. The term for that is called vapor pressure. Vapor pressure is reported in Pascals abbreviated Pa. To give you some idea of the ranges of vapor pressure; the molecule which makes up antifreeze, ethylene glycol, has a vapor pressure of 500Pa; water’s is 2300, and the propane gas in your gas grill 1,013,000 Pa. The higher the number the faster it evaporates. This is the basis for arranging notes from top to heart to base as differing vapor pressures means notes like aldehydes which have vapor pressures in the 10,000’s fly off first and the big synthetic molecules like Iso E super generally have vapor pressures in the 1,000’s. Now this is a simplistic comparison and the molecules which are used in perfumery also have other qualities which can make them persist a little longer than straight vapor pressure. For the purpose of this discussion the notes in perfume evaporate at different rates which form the development of a perfume on your skin.


Water Drop by John Kane

When and how you apply perfume will have a very large effect on how this evaporation occurs. If you add a single drop to each wrist it is in a concentrated spot and the evaporation will take place slower causing a slightly longer development of the perfume on your wrist. Now when you take your wrists and rub them together taking that drop and smearing it into a thin film you are now speeding up the evaporation much as when you spread out water when you mop the floor. A thin widely applied film evaporates much quicker. So as you rub your wrists together the combination of body heat and dispersion makes, especially the top notes, evaporate all that much quicker.

The molecules aren’t so much bruised as excited to get out into the atmosphere a lot quicker now that you’ve made it easier for them to escape. The difference in the way a perfume smells when applying to a wrist and rubbing has nothing to do with brutalizing the molecules.

So if you’ve refrained from rubbing your wrists together because you think you're abusing the poor molecules in your perfume don’t worry they are fine. The only thing you do when you rub your wrists together is alter the evaporation profile in favor of the lower vapor pressure components. Which if you aren’t fond of the top notes of a particular fragrance might be a benefit.

So much as Hannibal Lecter asked of Clarice Starling at the end of “The Silence of the Lambs” I hope you no longer hear the cries of the molecules the next time you rub your perfumed wrists together.

Mark Behnke